Laser Diagnostics Laboratory for Advanced Energy and Propulsion Research

Plasma Enhanced Combustion

Research in plasma enhanced combustion...

is dedicated to laser and optical diagnostics of plasma enhanced thermal oxidation for both flame enhancement and fuel reformation. Flame enhancement using plasma energy is potentially a critical technology which can be applied to hypersonic propulsion systems to achieve combustion stability in supersonic flow conditions.

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Non-equilibrium plasma for enhanced chemical energy conversion

By using a non-equilibrium plasma discharge, we can add energy to enhance the chemical energy conversion process without a significant deposition of heat. This leads to an increase in electrons, ions, and other chemical species in the reaction zone which can significantly accelerate the propagation and branching of radicals needed to achieve faster flame speeds and extended flammability limits.

Direct Plasma Energy Coupling

An effort is underway to investigate a direct plasma energy coupling strategy where an enhanced e-field is coupled into a pre-existing pilot flame. The electrons and radicals in the pilot flame interact with the e-field and ionization can occur at significantly lower powers. The left picture shows a custom built microwave plasma torch where the e-field can be focused into the tip of a torch and directly into the flame.

Supported by the Air Force Office of Scientific Research

Laser and Optical Imaging

Laser and optical diagnostics can be carried out in the flame to investigate the increase of chemical species and thermodynamics parameters. The right figure shows flame images as a function of microwave power, as well as PLIF images for OH and CO. It can be seen that a plasma plume can be generated with as little as 6 W of microwave power, where a dramatically increase in OH can also be observed. The CO was carried out using two-photon LIF and shows the impact of in-situ fuel reformation effects during the plasma energy coupling.

Direct Coupling for Various Geometries

Efforts are also being made to investigate the direct plasma energy coupling concept for a range of flame geometries. Th left side picture shows a new direct coupled microwave torch using a standing wave in tuning cavity. The microwave is picked up through a coaxial torch and the plasma is generated at the tip of the torch and coupled directly into the reaction zone.

Plasma system by Amarante Technologies

Supported by the Air Force Office of Scientific Research

Laser Imaging of Various Flame Configurations

The right picture shows the full figure of the torch as well as LIF imaging of OH radicals in a non-premixed flame configuration. The plasma and flame interaction is highly dependent on the combustion dynamics and efforts are being made to investigate the relative impact of the plasma, changes in chemistry, and changes in the efficiency of the coupling process for various flame configurations.

Plasma system by Amarante Technologies

New Efforts with Practical Ignition Systems

New research efforts will be made in the coming months to investigate actual implementation of a plasma discharge in a small engine (UAV class) with the Small Engines Division at Wright Patterson AFB, as well as implementation of a nanosecond direct current discharge in a opposed diffusion flame geometry for laser and optical diagnositcs.